WM8753 Wolfson Microelectronics plc, WM8753 Datasheet - Page 31

• Manufacturer Part Number: WM8753
• Description: HI FI AND TELEPHONY DUAL CODEC
• Manufacturer: Wolfson Microelectronics plc

WM8753L
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AUTOMATIC LEVEL CONTROL (ALC)
Figure 10 ALC Operation
The WM8753L has an automatic level control that aims to keep a constant recording volume
irrespective of the input signal level. This is achieved by continuously adjusting the PGA gain so that
the signal level at the ADC input remains constant. A digital peak detector monitors the ADC output
and changes the PGA gain if necessary.
Table 19 ADC Digital Volume Control
signal
signal
input
PGA
after
ALC
R16(10h)
Left ADC
Digital Volume
R17 (11h)
Right
Digital Volume
gain
REGISTER
ADDRESS
ADC
7:0
8
7:0
8
BIT
hold
time
LADCVOL
RADCVOL
[7:0]
LAVU
[7:0]
RAVU
decay
time
LABEL
11000011
( 0dB )
0
11000011
( 0dB )
0
attack
DEFAULT
time
Left ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -97dB
0000 0010 = -96.5dB
... 0.5dB steps up to
1111 1111 = +30dB
Left ADC Volume Update
0 = Store LADCVOL in intermediate latch
1 = Update left and right channel gains
Right ADC Digital Volume Control
0000 0000 = Digital Mute
0000 0001 = -97dB
0000 0010 = -96.5dB
... 0.5dB steps up to
1111 1111 = +30dB
Right ADC Volume Update
0 = Store RADCVOL in intermediate
1 = Update left and right channel gains
(no gain change)
(left = LADCVOL, right =
intermediate latch)
latch (no gain change)
(left = intermediate latch, right =
RADCVOL)
target
level
ALC
DESCRIPTION
AI Rev 3.1 June 2004
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